Impact of honey bee migratory management on pathogen loads and immune gene expression is affected by complex interactions with environment, worker life history, and season

Authors: Simone-Finstrom, Michael; STRAND, MICHELINE - Experimental Pathology Laboratories, Inc; TARPY, DAVID - North Carolina State University; RUEPPELL, OLAV - University Of Alberta

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2021
Publication Date: 2/7/2022
Citation: Simone-Finstrom, M., Strand, M.K., Tarpy, D.R., Rueppell, O. 2022. Impact of honey bee migratory management on pathogen loads and immune gene expression is affected by complex interactions with environment, worker life history, and season. Journal of Insect Science. 22(1):17. https://doi.org/10.1093/jisesa/ieab096.
DOI: https://doi.org/10.1093/jisesa/ieab096

Interpretive Summary: The effects of commercial management of honey bee colonies, particularly migratory beekeeping to fulfill necessary pollination services of many agricultural crops, are of ongoing debate concerning how or if the practice may contribute to current honey bee health issues. The direct impact of migratory practices on honey bee diseases are not well understood. To test the impacts of managed migration on disease loads and immunity, experimental honey bee colonies were either moved every 21 days to different agricultural areas to simulate migratory beekeeping or left in a stationary apiary. Samples at different ages and life history stages (hive bees or foragers), taken at the beginning and end of the active season, were analyzed for pathogen loads and physiological markers associated with health or stress. Overall, results of this study shed light on the complex interactions of bee management for commercial pollination services on bee health and the spread of pathogens. The findings that in some cases bees involved in migratory management (either during larval and pupal development or as adults) can increase prevalence of some viral infections, while gut parasite loads are reduced provides continued evidence that migratory management is a mix of costs and benefits. Additional research, with particular attention to effects during development, should be geared towards further understanding how these costs can be mitigated to more effectively improve bee health and thus our food security given the demands of agricultural pollination services.

Technical Abstract: The effects of management, such as intensive migratory beekeeping, are of ongoing debate concerning the causes of honey bee health problems. Even though comparisons of disease among differently managed colonies indicate some effects, the direct impact of migratory practices on honey bee diseases are not well understood. To test the long- and short-term impact of managed migration on disease loads and immunity, experimental honey bee colonies were maintained with or without migratory movement and individuals that experienced migration as juveniles (e.g., larval and pupal development), as adults, or both were compared to control colonies that remained stationary and therefore did not experience migratory relocation. Samples at different ages and life history stages (hive bees or foragers), taken at the beginning and end of the active season, were analyzed for pathogen loads and physiological markers associated with health or stress. Bees exposed to migratory management during adulthood had increased levels of the AKI virus complex (Acute bee paralysis, Kashmir bee, and Israeli acute bee paralysis viruses) and decreased levels of antiviral gene expression (dicer-like, hsp90). However, those in stationary management as adults had elevated gut parasites (Nosema and trypanosomes). Effects of environment during juvenile development were more complex and interacted with life-history stage and season. Age at collection, life-history stage, and season all influenced numerous factors from viral load to immune gene expression. Overall, these data shed light on the complexity of how management practices can influence individual bee exposure to pathogens, health, and resiliency.